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P0178..Flex fuel sensor??

Old March 17th, 2015, 9:03 PM
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Im having the same problem with my truck and it started a while back i thought it was the fuel pump ,should i try running it with flex fuel??? How can i find out if it runs with it or if it a non flex fuel I have a 2004 5.3 2wd vortec tahoe when i got it with 180,xxx miles i bought it from a dealership and it work fine gas saver too then out of nowhere i had fuel problems and started wasting gas i barely found out that 04 tahoe use flex fuel too...should i try it wirh flex fuel???? Were is the sensor located so i can clean it...i appreciate everybodys info God bless everybody
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Old March 20th, 2015, 12:08 PM
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Welcome to the forum...
I would NOT recommend running e-85 if you do not know if the engine is flex capable or not. You may need to have the alcohol reading reset if it is reading incorrectly...
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Old March 20th, 2015, 7:04 PM
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not sure what fault you are describing but if its running bad with regular fuel; using flex fuel won't make it better.
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Old October 31st, 2017, 10:19 AM
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Default ever fix this

Originally Posted by Rvaburb View Post
My 04' burb has the same issue! I keep clearing out the code and tapping on the sensor with a mallet and it goes off for a hundred miles or so. Then the light comes back on and also reads the knock sensors are bad. I had not thought of really running flex fuel. Gas around here just contains 10% ethonal is that the same thing?
Hey Rvaburb, wondering if you ever fixed this issue with your 04 burb and flex fuel sensor? I've been having the same flex fuel sensor issue on my 05 1500 suburban Z71 for some time, I get a P0179 code and I tap on the flex sensor and it goes away for a while. Recently had the same sold start issue that you had, it started and was running rich, gave me codes P0172 & P0175, I tapped on the flex sensor and it all cleared up again. I figure the PCM was trying to compensate for a bad reading from the flex fuel sensor and caused the rich condition. Like most I hate to replace the $400 flex sensor if I don't need too. Thx in advance for any help.

Last edited by Mr_MarkG; October 31st, 2017 at 10:22 AM.
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